Historical Foundation of Plant and Groundwater Interactions - Introduction to Phytoremediation of Contaminated Groundwater - page 16

alfalfa growth in the immediate area was observed to be
vigorous, and as the water table declined later in the season,
the plants appeared withered.
Figure 1.8 depicts the first published evidence of the
interaction between plants and groundwater, and this obser-
vation proceeds by more than 70 year the application of such
plants for the phytoremediation of contaminated groundwa-
ter. More importantly, because Meinzer and White were
hydrogeologists, they were perhaps the first scientists to

relate readily observable differences in plant morphology,
such as vigor, to less readily observable, hidden characteris-
tics that compose some of the fundamentals of hydrogeol-
ogy, such as depth to water table, thickness of the capillary
fringe, and the role that soil properties have in controlling
the bioavailability of water to plants. As such, their studies
provide a fundamental basis for plant and groundwater
interactions and, therefore, for the phytoremediation of
contaminated groundwater.
Such scientific observations also had economic implica-
tions. These investigations of Meinzer and White confirmed
the belief that a profitable cash crop could be grown in arid
conditions without costly, long-term irrigation. This notion,
in part, led the way to economic growth in the western
United States in the early twentieth century. Alfalfa is the
third most widely grown crop in the United States (circa
2007) and used for hay, seed production, alfalfa meal (for-
age), and honey. This direct evidence of plant and ground-
water interaction suggests a possible reason why alfalfa was
grown and cultivated in Persia, the location of modern-day
Iran, prior to the use of irrigation. Finally, alfalfa still can be
found to grow wild in parts of arid Africa.

1.2.4 Charles H. Lee and His Experiments

The observations of Meinzer and White were built upon
even earlier observations by another USGS colleague,
Charles H. Lee. Because of the role of groundwater in
controlling the types and distributions of plants in arid
regions, Lee was interested in determining what component
of the water budget was derived from the transpiration of
groundwater by native plants compared to evaporation from
surface soils. In his study of the water resources of Owens
Valley, California, he recognized that
... the roots of vegetation, such as wild grass, penetrate the soil

to groundwater and become the channels by which a large
amount of moisture is conveyed into the atmosphere. Evapora-
tion from bare soil combined with transpiration is in fact the
most important element entering into computations relating
groundwater for this region.

C.H. Lee (1912)

It is unclear whether or not he meant that the water was
conveyed to the surface through the plants by transpiration,
or outside of the roots through the channels.
In attempts to quantify the contribution of groundwater
transpiration by plants to total water losses that included soil
evaporation, Lee took a rather novel experimental approach.
He placed large metal tanks in the ground, filled them with
native soil, planted salt grasses, and created a constant artifi-
cial water-table surface in each tank through the addition
of carefully measured quantities of water from adjacent
reservoirs

Fig. 1.8 The first published observation of the direct interaction
between plants and groundwater, in particular the distribution of the
root system of alfalfa ( Medicago sativa ), a wild phreatophyte, and
depth to groundwater (the dated and dashed lines). The depth of the
water table controlled the depth of the roots and the health of the plant
(Modified from Meinzer 1927).

to account for losses by evaporation and